Avaliação e seleção de clones de capim-elefante sob pastejo de ovinos na zona da mata de Pernambuco

Abstract

This work aimed to evaluate the influence of morphological characteristics on tissue proportion and ruminal digestion of leaf blades of clones from elephantgrass, and also to study the genotype x environment interaction on morphological and productive characteristics, by stability and adaptability analyzing to select Pennisetum sp. clones under sheep grazing. The experiment was conducted at the Itambé Experimental Station of Pernambuco, Agricultural Research Institute - IPA, Dry Forest Zone of Pernambuco. Genotypes were managed under rotational stocking, being used 25 Santa Inês sheep in "mob grazing" to obtain residue height of 0.3 m. Morphological and productive evaluations were conducted between September 2008 and September 2010, totaling sixteen grazing cycles. There was difference among clones for nine grazing cycles to the leaf blade/stem ratio, with the dwarf clones showing a higher proportion of leaf blades. There was difference - in all grazing cycles - among the genotypes for the internode length, plant height and proportion of sclerenchyma, adaxial epidermis, bulliform cells, total vascular bundle, mesophyll, bundle sheath and number of vascular bundles of the leaf blade tissues of genotypes. The average herbage accumulation ranged from 2180 kg DM ha-1 (Taiwan 2.37) to 3383 kg DM ha-1 (Mott) and 2796 kg DM ha-1, the overall average. Dwarf genotypes Taiwan 2.27, Taiwan 2.114 and Mott showed high yielding capacity of leaves per tiller. The observed differences in morphological and anatomical characteristics among clones of different heights did not affect the rate of disappearance of leaf blade tissues after 48 h of ruminal digestion. Besides the high yielding of dwarf clones Mott and Taiwan 2.114, this accumulation of forage is represented by a greater number of leaves, and is therefore recommended for next phase of the breeding program.